The present invention relates to the automated scoring of so-called “bubble” forms or the like, whereby each of a multiplicity of end users such as students, voters, and questionnaire respondents, enters marks on a standard form associated with the individual, to indicate the specific choices from among those offered on the form. The marks are typically entered by darkening (filling in) preprinted circles or ellipses with a pencil. Inevitably, some of the respondents apply very light pressure on the pencil and therefor produce a very light mark. The marks made by other respondents may either extend out of the designated target, or partially within and partially outside of the target. In other cases, a stray mark may inadvertently be made near a target. These deviations give rise to the need for interpretation of the intent of the user. This is in addition to deviations that arise from imperfect printing of the form, and misalignment or bending of the form as it passes through the scoring system.
Under the present state of the art, bubble forms are processed with highly specialized scanners that sense the marked state of the bubble targets using a fixed array of LED sensors. These scanners do not work by producing an electronic image reproduction of the contents of the forms; they merely sense the darkness levels of certain predefined fixed locations of the forms. On a form page of dimension 8½×11 inches, the typical bubble density is approximately six bubbles per inch in each of the page dimensions. This is similar to the LED sensor density and thus, one LED sensor is associated with each column of bubble locations. In order to achieve and maintain their accuracy rates, these scanners require extremely high quality paper with very precise printing and cutting. Production of such forms is very expensive and is usually available only from a single source, namely, the same company that produces the LED scanner.